Endocrine System
Glands — pituitary, thyroid, adrenals, pancreas, gonads — that release hormones into the blood to regulate growth, metabolism, stress, blood sugar, and reproduction.
Compared with the nervous system, endocrine signaling is slower but longer-lasting and reaches every tissue with a receptor. Most hormones are governed by negative feedback — the response shuts off further release, as when rising thyroid hormone suppresses the pituitary’s TSH.